Cells such as myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), regulatory T cells (Tregs), fibroblasts, and mast cells are upregulated in the TME, ultimately protecting tumor cells from being eliminated by the immune system; on the other hand, natural killer (NK) cells and CD8+ T cells that act to destroy tumor cells are downregulated [22]. The gene discussed is CD8A; the disease is neoplasm.